scholarly journals Phantom of RAMSES (POR): A new Milgromian dynamics N-body code

2015 ◽  
Vol 93 (2) ◽  
pp. 232-241 ◽  
Author(s):  
Fabian Lüghausen ◽  
Benoit Famaey ◽  
Pavel Kroupa
Keyword(s):  
Dark Matter ◽  
Dynamical Systems ◽  
Spatial Resolution ◽  
Gas Dynamics ◽  
Adaptive Mesh Refinement ◽  
High Spatial Resolution ◽  
Large Range ◽  
Adaptive Mesh ◽  
Scaling Relations ◽  
Disk Galaxies

Since its first formulation in 1983, Milgromian dynamics (MOND) has been very successful in predicting the gravitational potential of galaxies from the distribution of baryons alone, including general scaling relations and detailed rotation curves of large statistical samples of individual galaxies covering a large range of masses and sizes. Most predictions, however, rely on static models, and only a handful of N-body codes have been developed over the years to investigate the consequences of the Milgromian framework for the dynamics of complex evolving dynamical systems. In this work, we present a new Milgromian N-body code, which is a customized version of the RAMSES code (R. Teyssier. Astron. Astrophys. 385, 337 (2002). doi:10.1051/0004-6361:20011817 ) and thus comes with all its features: it includes particles and gas dynamics, and importantly allows for high spatial resolution of complex systems owing to the adaptive mesh refinement technique. It further allows the direct comparison between Milgromian simulations and standard Newtonian simulations with dark matter particles. We provide basic tests of this customized code and demonstrate its performance by presenting N-body computations of dark-matter-free spherical equilibrium models as well as dark-matter-free disk galaxies in Milgromian dynamics.

scholarly journals DARK MATTER HALOS AND EVOLUTION OF BARS IN DISK GALAXIES: VARYING GAS FRACTION AND GAS SPATIAL RESOLUTION

2010 ◽  
Vol 719 (2) ◽  
pp. 1470-1480 ◽  
Author(s):  
Jorge Villa-Vargas ◽  
Isaac Shlosman ◽  
Clayton Heller
Keyword(s):  
Dark Matter ◽  
Spatial Resolution ◽  
Disk Galaxies ◽  
Dark Matter Halos

scholarly journals Hydrodynamical Adaptive Mesh Refinement Simulations of Disk Galaxies

2008 ◽  
Vol 4 (S254) ◽  
pp. 445-452
Author(s):  
Brad K. Gibson ◽  
Stéphanie Courty ◽  
Patricia Sánchez-Blázquez ◽  
Romain Teyssier ◽  
Elisa L. House ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Adaptive Mesh Refinement ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Disk Galaxies ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Temporal And Spatial ◽  
Compare And Contrast

AbstractTo date, fully cosmological hydrodynamic disk simulations to redshift zero have only been undertaken with particle-based codes, such as GADGET, Gasoline, or GCD+. In light of the (supposed) limitations of traditional implementations of smoothed particle hydrodynamics (SPH), or at the very least, their respective idiosyncrasies, it is important to explore complementary approaches to the SPH paradigm to galaxy formation. We present the first high-resolution cosmological disk simulations to redshift zero using an adaptive mesh refinement (AMR)-based hydrodynamical code, in this case, RAMSES. We analyse the temporal and spatial evolution of the simulated stellar disks' vertical heating, velocity ellipsoids, stellar populations, vertical and radial abundance gradients (gas and stars), assembly/infall histories, warps/lopsideness, disk edges/truncations (gas and stars), ISM physics implementations, and compare and contrast these properties with our sample of cosmological SPH disks, generated with GCD+. These preliminary results are the first in our long-term Galactic Archaeology Simulation program.

scholarly journals On the accretion history of galaxy clusters: temporal and spatial distribution

2020 ◽  
Vol 499 (2) ◽  
pp. 2303-2318
Author(s):  
David Vallés-Pérez ◽  
Susana Planelles ◽  
Vicent Quilis
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Temporal And Spatial Distribution ◽  
Mass Growth ◽  
Accretion Flows ◽  
Novel Approach ◽  
Mass Assembly ◽  
Gas Accretion

ABSTRACT We analyse the results of an Eulerian adaptive mesh refinement cosmological simulation in order to quantify the mass growth of galaxy clusters, exploring the differences between dark matter and baryons. We have determined the mass assembly histories (MAHs) of each of the mass components and computed several proxies for the instantaneous mass accretion rate (MAR). The mass growth of both components is clearly dominated by the contribution of major mergers, but high MARs can also occur during smooth accretion periods. We explored the correlations between MARs, merger events, and clusters’ environments, finding the mean densities in 1 ≤ r/R200m ≤ 1.5 to correlate strongly with Γ200m in massive clusters that undergo major mergers through their MAH. From the study of the dark matter velocity profiles, we find a strong anticorrelation between the MAR proxies Γ200m and α200m. Last, we present a novel approach to study the angularly resolved distribution of gas accretion flows in simulations, which allows to extract and interpret the main contributions to the accretion picture and to assess systematic differences between the thermodynamical properties of each of these contributions using multipolar analysis. We have preliminarily applied the method to the best numerically resolved cluster in our simulation. Amongst the most remarkable results, we find that the gas infalling through the cosmic filaments has systematically lower entropy compared to the isotropic component, but we do not find a clear distinction in temperature.

scholarly journals A High Spatial Resolution X‐Ray and Hα Study of Hot Gas in the Halos of Star‐forming Disk Galaxies. II. Quantifying Supernova Feedback

2004 ◽  
Vol 606 (2) ◽  
pp. 829-852 ◽  
Author(s):  
David K. Strickland ◽  
Timothy M. Heckman ◽  
Edward J. M. Colbert ◽  
Charles G. Hoopes ◽  
Kimberly A. Weaver
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Disk Galaxies ◽  
X Ray ◽  
Star Forming ◽  
Hot Gas ◽  
Supernova Feedback

scholarly journals Star Formation in Large N Clusters

2002 ◽  
Vol 207 ◽  
pp. 489-498 ◽  
Author(s):  
C.J. Clarke
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Dynamical Systems ◽  
Globular Cluster ◽  
Gas Dynamics ◽  
Cluster Formation ◽  
Dynamical Evolution ◽  
Initial State ◽  
Large N ◽  
Young Clusters

We focus here on the gas dynamics of cluster formation and the early stellar dynamical evolution of young clusters. We point out that the condition that a cloud can fragment into a large number of pieces places rather particular constraints on its initial state; we also review the processes that shape the stellar IMF in cluster formation simulations. We show how N-body calculations and observations can be combined to discover the properties of clusters at the point at which they first become stellar dynamical (as opposed to gas dynamical systems). Finally, we touch on the question of how proto-cluster clouds are assembled and reopen the issue of whether dark matter may play a role in globular cluster formation.

scholarly journals The Structure of Cold Dark Matter Halos

1996 ◽  
Vol 171 ◽  
pp. 255-258 ◽  
Author(s):  
Julio F. Navarro
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Large Range ◽  
Disk Galaxies ◽  
Dark Matter Halos ◽  
Density Profiles ◽  
Halo Structure ◽  
Disk Rotation ◽  
Disk Mass ◽  
The Masses

High resolution N-body simulations show that the density profiles of dark matter halos formed in the standard CDM cosmogony can be fit accurately by scaling a simple “universal” profile. Regardless of their mass, halos are nearly isothermal over a large range in radius, but significantly shallower than r–2 near the center and steeper than r–2 in the outer regions. The characteristic overdensity of a halo correlates strongly with halo mass in a manner consistent with the mass dependence of the epoch of halo formation. Matching the shape of the rotation curves of disk galaxies with this halo structure requires (i) disk mass-to-light ratios to increase systematically with luminosity, (ii) halo circular velocities to be systematically lower than the disk rotation speed, and (iii) that the masses of halos surrounding bright galaxies depend only weakly on galaxy luminosity. This offers an attractive explanation for the puzzling lack of correlation between luminosity and dynamics in observed samples of binary galaxies and of satellite companions of bright spiral galaxies, suggesting that the structure of dark matter halos surrounding bright spirals is similar to that of cold dark matter halos.

scholarly journals Vector modes in ΛCDM: the gravitomagnetic potential in dark matter haloes from relativistic N-body simulations

2021 ◽  
Author(s):  
Cristian Barrera-Hinojosa ◽  
Baojiu Li ◽  
Marco Bruni ◽  
Jian-hua He
Keyword(s):  
Dark Matter ◽  
Adaptive Mesh Refinement ◽  
Gravitational Force ◽  
Percent Level ◽  
Adaptive Mesh ◽  
Velocity Fields ◽  
The Core ◽  
Transverse Modes ◽  
General Relativistic ◽  
The Impact

Abstract We investigate the transverse modes of the gravitational and velocity fields in ΛCDM, based on a high-resolution simulation performed using the adaptive-mesh refinement general-relativistic N-body code gramses. We study the generation of vorticity in the dark matter velocity field at low redshift, providing fits to the shape and evolution of its power spectrum over a range of scales. By analysing the gravitomagnetic vector potential, which is absent in Newtonian simulations, in dark matter haloes with masses ranging from ∼1012.5 h−1M⊙ to ∼1015 h−1M⊙, we find that its magnitude correlates with the halo mass, peaking in the inner regions. Nevertheless, on average, its ratio against the scalar gravitational potential remains fairly constant, below percent level, decreasing roughly linearly with redshift and showing a weak dependence on halo mass. Furthermore, we show that the gravitomagnetic acceleration in haloes peaks towards the core and reaches almost 10−10  h cm/s2 in the most massive halo of the simulation. However, regardless of the halo mass, the ratio between the gravitomagnetic force and the standard gravitational force is typically at around the 10−5 level inside the haloes, again without significant radius dependence. This result confirms that the gravitomagnetic effects have negligible impact on structure formation, even for the most massive structures, although its behaviour in low density regions remains to be explored. Likewise, the impact on observations remains to be understood in the future.

Pop III Supernova Feedback on the Formation of the First Galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 253-256 ◽  
Author(s):  
Li-Hsin Chen ◽  
Ke-Jung Chen
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Initial Conditions ◽  
Adaptive Mesh ◽  
Building Blocks ◽  
Dark Matter Halos ◽  
First Stars ◽  
Stellar Feedback ◽  
First Galaxies

AbstractModern cosmological simulations suggest that the hierarchical assembly of dark matter halos provided the gravitational wells that allowed the primordial gases to form stars and galaxies inside them. The first galaxies comprised of the first systems of stars gravitationally bound in dark matter halos are naturally recognized as the building blocks of early Universe. To understand the formation of the first galaxies, we use an adaptive mesh refinement (AMR) cosmological code, Enzo to simulate the formation and evolution of the first galaxies. We first model an isolated galaxy by considering much microphysics such as star formation, stellar feedback, and primordial gas cooling. To examine the effect of Pop III stellar feedback to the first galaxy formation, we adjust the initial temperature, density distribution and metallicity distributions by assuming different IMFs of the first stars. Our results suggest that star formation in the first galaxies is sensitive to the initial conditions of Pop III supernovae and their remnants. Our study can help to correlate the populations of the first stars and supernovae to star formation inside these first galaxies which may be soon observed by the (James Webb Space Telescope JWST).

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